Smitten with Sin
by Thundercatlost
Summary: After being recruited by the chief detective at a detective agency, Shuichi Saihara willingly takes on the challenge of catching and identifying a mysterious and intelligent phantom thief. Unfortunately, things don't quite go according to plan. [Saiouma/Oumasai Phantom Thief AU. Rated T for gore, dark themes and romance. Contains a little bit of Naegiri and Komahina.]


_**Hello!**_

 ** _Welcome to my brand new story: Smitten with Sin. I haven't actually uploaded any Danganronpa fanfictions on my account yet so here's to my new addiction!_**

 ** _As mentioned in the description, this is a Saiouma/Oumasai Detective Agency AU. To elaborate further, Shuichi is the newest recruit at a detective agency and Kokichi is a phantom thief. This isn't a killing game but that doesn't mean there won't be any death... Hehehe. ;)_**

 ** _I'm awful at writing comedy so I hope I at least get you to smile!_**

 ** _Forgive me if anybody is OOC; I've only ever written about Kiibo, Kokichi and Nagito. I have played all four games so hopefully everyone isn't too awfully-written._**

 ** _For anybody new to my account, everything written in italics is a thought and everything bold and underlined is a title or time jump._**

 _ **I adore receiving reviews! Feel free to speculate what you think is going to happen next - it always excites me to see your theories and reactions.**_

 _ **This chapter is going to be incredibly fast-paced, unlike the rest of the story. That's purely because this chapter is just setting up the scene and introducing the main characters, along with their roles. The rest will be longer and more action-packed.**_

 _ **Enjoy! :D**_

* * *

 **Saturday 1st September 4pm - Present Day / POV: Shuichi Saihara**

Shuichi was nervously pacing around his office, his pocket-sketchbook and pencil gripped firmly in his hands. Today was his first day working as a detective and he had been (and still was) worriedly anticipating his first case.

He didn't really know any of his colleagues and hadn't spoken a word to any of them since arriving about an hour ago. Within that time, he had hurriedly unpacked his boxes of equipment and had just fidgeted impatiently around the room. Drips of anxiety and dread had begun to creep into his thoughts, trying to convince him that he was going to be unsuccessful at solving whatever mysteries awaited him. However, he managed to temporarily push these thoughts to the back of his mind by sketching some anime-style characters in his plain blue sketchbook.

"Shuichi Saihara?"

The young male turned around to see his boss waiting patiently by the door.

"Yes, Ms Kirigiri?" He replied, quickly standing up while somehow retaining a relaxed composure. He immediately stood up with a small smile, attempting to hide the nervousness that was flooding in once again.

"You're required for the next meeting. Please, follow me." She pivoted back to the door, turning her head back to look at him for a moment before walking down the corridor, saying: "Also, feel free to just call me Kyoko." As he shoved his pencil into his pocket, Shuichi quickly, yet somehow calmly, followed after her.After about thirty seconds of walking down corridors, they came to a room with a large dining table with name-tags neatly set out by each chair. After locating his own seat and sitting down, Saihara glanced around the room, looking at each person's name-tag:

 _'Mrs Kyoko Kirigiri, Head of Investigations'_ _'Miss Miu Iruma, Forensic Scientist'_ _'Miss Aoi Asahina, Accountant'_ _'Miss Chiaki Nanami, Detective'_ _'Mr Makoto Naegi, Head of Fire Department'_ _'Mr Gundam Tanaka, Head of Police Department'_ _'Miss Sonia Nevermind, International Spy'_ _'Mr Rantaro Amami, Journalist'_ _'Mr Hajime Hinata, Detective'_ _'Mr Shuichi Saihara, Detective'_

After locating his seat, he sat down and began to nervously twiddle his thumbs. He had been unable to ask his friends for advice, due to the case being "a private and confidential matter that only the highest rank of detectives are allowed to partake in.", to quote Kyoko's words. Obviously, the pressure did little to ease his fear. Although, he was quite pleased with where he was sat - on one sit of him was Kyoko and on the other was another detective. _Perhaps, she's arranged my seating next to this 'Hajime Hinata' intentionally...?_

He watched in silence as Kyoko took her seat, swiftly darting her eyes towards his. He blinked a few times as the situation began to sink in that little bit deeper.

Shuichi had literally only solved one case in his life. It was a murder mystery that he had miraculously managed to solve before the police because he managed to point out a lie in the suspect's statement. Being incredibly inexperienced and uncertain, he'd actually attempted to decline the offer at first of being allowed to join the Detective team. Despite it being a childhood dream of his, his lack of self-esteem had almost managed to push his dreams down into much, much deeper corners of his consciousness. In fact, if it wasn't for his encouraging friend Kaito, who had attempted (and failed) to assist in boosting Shuichi's skills, he probably would have just given it up altogether.

A loud slam as the door bust open managed to snap Shuichi back to reality. A blonde-haired girl wearing a formal pink dress strutted into the room. Upon her face was a look of pure annoyance as she muttered something about formality being absolute rubbish. That was until she noticed Shuichi sat at the table. A wide grin spread across her face.

"GOD, KYOKO! YOU'VE HIRED ANOTHER PERV!" The girl laughed hysterically in an amused fashion.

"E-Excuse me?" Saihara stammered. Whoever this person was, he already knew he wasn't going to get along with her.

"Miu Iruma, Shuichi is not a pervert. He is our new detective. Now please sit at the table and stop complaining." Kyoko flatly instructed her.

 _Ah, so this must be Miu Iruma, the forensic scientist. Kyoko's usage of her full name probably means they aren't exactly on perfect terms._

"Ugh, fine! I'd better be paid tonight or I'm going to f-"

"Please, Miu. Do not babble about the inconsistencies while exploiting your own foul language that even my demons are wary of." Came another voice from down the hallway. A tall man wearing a black suit and tie emerged through the door, who, to Shuichi's surprise, had four hamsters upon his shoulders, each having almost an eerie atmosphere around them. He located his seat and sat down, receiving an irritated glare from Miu.

'Mr Gundam Tanaka, Head of Police Department'

He was quickly followed by a brunette who wore a white shirt and a crimson-red skirt. "Hey, guys! I bought donuts but...uhh..."

A light smile graced Kyoko's lips. "You ate them all again, didn't you?"

The brunette pouted. "Yeah..."

Chuckling quietly, Kyoko lifted something out from underneath the table. "Don't worry; I made sure to buy some extra donuts before we came."

One after another, more and more people seemed to enter the room and found their allocated spot. After a few minutes, all of the seats were filled and Shuichi had used his notebook to jot down his opinions on each person.

 _Aoi is bubbly but she's not too bad. Gundam is incredibly confusing but he doesn't seem like a bad person. Chiaki seems intelligent but she's literally falling asleep at the table. Miu is...let's not go there. Makoto seems like the most average out of the lot. Sonia is very elegant, calm and collected yet outgoing - exactly what I expect from an international spy. Rantaro seems relaxed, possibly because being a journalist is probably the easiest job out of the lot. Either that for hes just genuinely a relaxed person._

Last but not least is Hajime Hinata. Hajime kept talking to the others while occasionally shooting an encouraging glance towards Saihara. It was almost as if Hajime knew exactly how nervous Shuichi was.

 _He seems like a decent person._

"Okay, now that everybody has gathered here, I think it's best if we introduce our newest detective, Shuichi Saihara." Kyoko turned her head to look at Shuichi and the others followed suit. "I personally invited him to work here, so I expect you all to treat him well."

"Welcome to the team, fellow detective." Hajiime smiled and held out his hand, which Shuichi gratefully shook back. "I hope you settle in well."

"More like: 'Welcome to the madhouse, fellow nutcase!'" Miu joked, only to be nudged in the shoulder by a stern Kyoko.

"I agree with Hajime; it's always nice to have a new recruit." Sonia waved. "My apologies if Miu is making you uncomfortable. She's always a bit of a...what's the word...b-?"

"Hey, Shuichi!" Aoi called out, cutting Sonia off. She suddenly pushed a closed cardboard box down the table towards him. "Have a donut! Just don't eat them all or the Cookie Monster will come and eat you up!"

"T-Thanks." He stuttered, opening the box. Inside was an array of donuts. Each one of them was iced with yellow icing and topped with pink sprinkles. He cautiously took one out and bit into it. The sickly-sweet taste of sugar filled his senses and it managed to calm his nerves a little.

"So, Kyoko, what's on today's agenda?" Makoto asked, wrapping an arm around her shoulder. The two of them appeared very close - he scribbled that down in his notebook.

"We need to locate the masked criminal's next planned robbery."

Unintentionally smiling, Shuichi found that his eyes lit up and all of his fear vanished into thin air.

"You're talking about the masked criminal in all of the newspapers, right? The one who managed to steal a diamond without getting caught?" Shuichi asked, just to make sure he was on the right page.

For the last month, every newspaper had a little section dedicated to the robberies that had been committed by a "fast, masked criminal". It first started four weeks ago, when they managed to steal a safe from somebody's mansion. A week later, the same person had supposedly managed to steal a _very beautiful_ famous pianist's grand piano. The following week, they had miraculously stolen every painting in an art museum and last week, they had taken a pop idol's golden microphone. They were known for their all-white outfit and silver mask, though their supposed outfit could be entirely made up, due to the lack of information about them. Not only did they hide their face, they also never spoke, thus nothing about them was known, not even knew their gender. Nobody had ever been able to get close enough to them in order to take a picture. This mysterious case had peaked Saihara's interest and he could list almost all of the known details of the crimes.

"Correct. These robberies have been going on for a month and every time, their crimes get more ambitious. We need to catch them before any further thieving attempts take place." Kyoko seemingly acknowledged Shuichi's interest and knowledge on the subject and gave him a pleased nod.

"I say that we just let 'em continue. Serves those rich people right for not sharin' their money with this gorgeous girl genius!" Miu added her own little self-praise into the conversation.

"Are their any previous scenes that you haven't investigated?" Makoto asked, ignoring Miu's remark.

"I checked the site of the last crime and I figured something out that might be useful...I think." Chiaki stated.

"Your advice is sure to lead us out of the fires of pandemonium! Let us hear what you have unearthed from the realm of stolen artefacts, Chiaki!" Gundam insisted.

"The thief keeps going for heavily-guarded places to the left of their previous incident. The locations are also getting gradually further away from this station and the crimes always take place at some point between 8pm and 9pm."

Miu blinked a few times before speaking. "Why the hell would somebody choose to go to places that were heavily-guarded? Surely having more guards would make them want to rob them less!"

"I think the more urgent question is why they always go the places on their left that are further away from the station." Sonia pointed out.

"It might just be habit." Rantaro put a hand on his chin as he pondered. "What's to the left of Miss Maizono's house, again?"

 _Ah, that's right. The last robbery was the stolen golden microphone that belonged to one of the most popular pop-idols in the country: Sayaka Maizono._

"There's that donut shop I love. Oh, and the confectionery store!" Aoi began to list all of the places she adored. "There's the supermarket - their donuts are pretty good - then there's the restaurant, the toy store, the old jewellery museum where they're holding that fashion contest tonight, the theatre, the cats and dogs home... It could be anywhere! There's no way of knowing for sure!"

"NO, THAT'S WRONG!" Makoto slammed a hand down on the table. He immediately regretted that decision as Asahina seemed rather startled by the sudden reaction. "Whoops, didn't mean to be that loud. I was just thinking...what if the masked criminal's next attack is at the old jewellery museum?"

"Didn't Hina just say that there was a fashion contest on?" Rantaro said.

"If the thief really is looking for danger, doing something while the area is full of crowds wouldn't be abnormal behaviour for them." Shuichi confirmed, jotting down some more notes in his notebook.

"I think it's fair to assume this will be their next place of attack. And, if what Chiaki has said is true, they should begin the robbery at between 8pm and 9pm." Kyoko smiled. "Gundam, could you alert some of your officers to stay on guard around that area that night?"

"Of course! My Four Dark Devas of Destruction will also assist us in thwarting the fiend's schemes!" And, as strangely as he had entered, he left, laughing in a deep and energetic voice. _What a strange man._

"Well, it seems that you didn't need my assistance this time!" Iruma put her hands on her hips as she stood up.

Rantaro grinned and whispered: "I don't think we have ever needed your assistance."

The blonde girl growled was obviously deeply offended by Amami's remark as she quickly headed down the corridor. _She's definitely only here for the money._

One by one, everybody began to leave the table to prepare, until all that was left was Kyoko, Hajime and Shuichi. Saihara was unsure as to whether he should leave or if Kyoko had something else to say.

Apparently she did.

"As you seem to know about this masked criminal's themes, perhaps you would like to accompany Hajime to the Jewellery museum...?"

Nodding his head, he caught sight of Hajime staring at the door. Following his gaze, Shuichi noticed that Makoto was weirdly hanging around in the corridor. _Perhaps Makoto is waiting for somebody?_

"I'm going to leave you three to it. I'll be waiting to hear an exact recount of what happened in tomorrow's report, Rantaro." With a click of her pen, Kyoko then wandered out of the room. Watching intently, Shuichi observed as Makoto met up with her and the duo disappeared down the corridor.

 _Something is definitely going on between those two._

"Hey, Shuichi, are you okay?" Saihara snapped to attention as Hajime spoke, a reassuring smile upon his face. A half-eaten donut was in in his hand and Amami looked up from the journal he was writing in. "I know it's kinda new to you but...I'm sure you'll manage to get to know everybody eventually. We're all friendly here; we aren't sex-crazed lunatics. Well, with the exclusion of Miu, but you get the idea." He joked.

"Yeah, don't stress yourself." Rantaro pitched in. "I'm sure Kyoko knows what she's doing."

Shuichi took a deep breath before speaking. "I'm so incredibly nervous. I've always investigated things on my own, never with other people."

"Heh, that's pretty ironic." Hajime took another bite from his donut before continuing. "Neither have I."

The three continued to talk to each other for about ten minutes. The conversation was a load of gossip about their home lives and the stressful talk of the supposed robbery tonight. Shuichi actually managed to find out some things about these two.

From what he could gather, Hajime was married to another man who had some sort of twisted obsession with hope and bagels. Hajime had devoted all of his time to detective work, similarly to Shuichi, but his husband didn't approve. The way Hinata was talking about his husband made Shuichi question, on multiple occasions, whether the married couple were actually happy in their small apartment together or not. On the other hand, Rantaro lived in a mansion with his sister and was actually one of the victims of the robberies, which is why he became a journalist. He had a part-time job as a teacher and he was a nail-artist in his spare time. As for the robbery later tonight, the trio of them decided that they would get there at 5:50pm, which gave them ten minutes beforehand to get their equipment prepared.

Beginning to finally fully relax, Shuichi felt like he'd gained a lot of confidence.

Little to his knowledge, that night was about to affect his entire life and that new-found wall of courage was about to crumble to the ground, piece by piece...


End file.
